For me it has:
*Good replay-ability value -} different branching paths, reasons to experiment and the game encourages you to try different choices and make mistakes
*Great graphics -} beautiful renders, the female characters have realistic\natural body form (which is awesome in my taste, unlike all those exaggerated body types in other games, that shit turns me off instantly. I don't even bother trying such games.)
*The story is interesting enough (obviously, unrealistic, it is a fantasy after all.) and the characters have some background, personal preferences and tastes, which makes them worthwhile to read through and understand. That truly enriches the experience for me. (unlike certain scenarios which are more like "omg i wanna fuck my daddy" with no reasoning given.)
*The corruption is relatively gradual and realistic. The buildup is half the fun for me - seeing the characters around you getting accustomed to your goals and ideas, slowly giving up resistance, and acting more freely in intimate situations.
I don't care for music, it is usually shitty in porn\eroge\hentai games anyways. So that saves me the trouble of needing to turn it off, I like playing with music that I actually like in the BG.
Sure, animation is always a plus, but it's not a must. I enjoy it more or less the same as long as the renders are good enough, and most animated games trade off the render quality to increase work speed. So animation is not a win-win thing in independent games.
So in my book, this game is definitely worth my money and attention.